The Institute of Electrical and Electronics Engineers (IEEE) has developed a comprehensive International Standard for Local Area Networks (LANs) employing Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as the access method. The IEEE standard is intended to encompass several media types and techniques for signal rates from one megabit per second (1 Mb/s) to ten thousand megabits or ten gigabits per second (10,000 Mb/s or 10 Gb/s). The IEEE standard introduces an Open Systems Interconnection (OSI) reference model that includes a number of layers. The layer that is of interest in this discussion is the physical layer which is located between the transmission medium and the data link layer. For 1000 Mb/s, for example, between the medium and the data link layer there is defined a medium dependent interface (MDI), a physical layer device (PHY), an optional gigabit media independent interface (GMII), and a reconciliation sublayer. The physical layer device is defined as including a physical medium dependent (PMD), a physical medium attachment (PMA), and a physical coding sublayer (PCS). The physical layer device is covered by the Access Method and Physical Layer Specification IEEE Std 802.3.
Although not covered by the current IEEE standard, the next order of magnitude improvement for twisted pair cable would be to advance to ten gigabits per second (10 Gb/s) in a communications protocol such as 10GBASE-T Ethernet. This however raises a whole new set of questions as the technology is pushing the transmission medium to its physical limits. Implementation issues that have not arisen before or at least not to such a degree will likely have to be addressed. An integral part of successful communications is a quality transmission medium. In terms of the protocol, the best available cable will likely be chosen when the choice is to be made. Practically speaking however, that cable might not always be used in the field. In the case of 10GBASE-T which is not set at this time, the preferred cable is likely to be Category 7 (CAT-7) double shielded twisted pair conductors. The specified length is likely to be one hundred meters. However, some forms of lesser cables such as CAT-6 and even CAT-5 might be actually used or even specified over shorter distances. Given the new implementation issues, it would therefore be beneficial for the physical layer device to be capable of performing cable diagnostics on the transmission medium.